1. Field of the Invention
The present invention relates to a lens component which is to be incorporated particularly in an optical system, and an image forming optical system using the lens component, and to an electronic image pickup apparatus such as a video camera and a digital camera having this image forming optical system.
2. Description of the Related Art
With the degree of maturation of the market of electronic image pickup apparatuses such as digital still cameras and video cameras, balancing of functional specifications has strongly been sought to even higher level. Here, the functional specifications are small size, slimness, light weight, low cost, and high image quality etc. From among the functional specifications, for the light weight, using an organic optical material having a low specific gravity in designing of an optical system has been taken into consideration, and has been used in some of the products.
However, since the organic optical materials have a problem of design constraints such as (i) the change in properties with respect to the temperature change is substantial as compared to that of glass, (ii) low refractive index, and (iii) when combined with glass, a difference in coefficient of expansion with that of glass is substantial, it has not yet been introduced proactively.
In most of the cases in which an organic optical material is used in an image forming optical system, the organic optical material is introduced in the last lens unit. This is because the last lens unit is a lens unit having a small effect paraxially or on aberration. There are also examples in which an organic optical material has been introduced proactively while taking into consideration properties of organic optical material as in embodiments described in Japanese Patent Application Laid-open Publication Nos. Hei 6-273670, 2005-128194, and 2008-310133.